From a transactional point of view, composite systems are component based applications in which each component has its own transaction management logic.These systems are highly relevant in practice since they are likely to be the standard architecture for many future distributed applications.Unfortunately,there is no appropriate conceptual framework in which to reason about such systems.Following up on existing work that addressed special cases of composite systems, in this paper we tackle the problem of general composite systems, i.e., those with arbitrary configurations.We propose a correctness criterion, develop a new proof technique that allows us to address arbitrary configurations, and discuss several important issues related to concurrency control in distributed systems.

In recent years, databases have started to be used as intelligent repositories for a variety of semantically-richer systems. A consequence of such architectures is that transaction scheduling takes place throughout composite systems consisting of layered subsystems. Such transaction architectures have been studied extensively. Existing theory, however, limits the degree of parallelism, and makes a number of simplifying assumptions which cannot be taken for granted in practice. This paper proposes a new model and correctness criterion, stack conflict consistency, for composite transactional systems. The main contribution of the new model is to establish the correctness conditions under which higher degrees of parallelism can be achieved between operations of the same transaction, as well as between conflicting operations of different transactions, in a uniform way. This possibility, although hinted at previously, has not yet been exploited in practical composite systems. Hence, we hope...